<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /*（1）利用绝对定位的方式，左右两栏设置为绝对定位，中间设置对应方向大小的margin的值。*/
    .outer {
      position: relative;
      height:100px;
      background-color: pink;
    }
    .left {
      position: absolute;
      width: 100px;
      height:100px;
      background-color:tomato;
    }
    .right {
      position: absolute;
      top: 0;
      right: 0;
      width: 200px;
      height:100px;
      background-color:gold
    }
    .middle {
      margin: 0 200px 0 100px;
      height:100px;
      background-color:lightgreen;
    }
  </style>
</head>
<body>
  <div class="outer ">
    <div class="left">left</div>
    <div class="middle">middle</div>
    <div class="right">right</div>
  </div>
</body>
</html>